Enhanced slice prediction feedback

ABSTRACT

Enhanced slice prediction is based upon ATSC VSB data when robust 8 VSB data are not available and is based upon robust 8 JSB data when robust 8 VSB data are available.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/198,014, filed Apr. 18, 2000, U.S. ProvisionalApplication No. 60/255,476, filed Dec. 13, 2000, and U.S. ProvisionalApplication No. 60/255,464, filed Dec. 13, 2000.

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to the transmission and/orreception of digital data.

BACKGROUND OF THE INVENTION

[0003] The standard in the United States for the transmission of digitaltelevision signals is known as 8 VSB data (ATSC Digital TelevisionStandard A/53). This 8 VSB data has a constellation consisting of eightpossible symbol levels. In a VSB system, the eight possible symbollevels are all in the same phase. In a QAM system, however, the symbolsare transmitted in phase quadrature relationship.

[0004] The standard referred to above specifies the formatting andmodulation of digital video and audio data. The transmitted data is inthe form of symbols with each symbol representing two bits of data thatare trellis encoded into three bits of trellis encoded data. Each threebits of trellis encoded data are mapped into a symbol having acorresponding one of eight levels. Reed/Solomon encoding andinterleaving are also provided to increase the robustness of thetransmitted information.

[0005] Auxiliary data (data other than digital video or audio data) arealso permitted to be transmitted in a digital television channel. Thesedata are formatted and modulated according to the standard in the samemanner as video and audio data. Receivers made in accordance with the 8VSB standard are able to read packet identifications (PIDs) which allowthe receivers to differentiate between audio, video, and auxiliary data.

[0006] However, while the robustness of the transmitted digitaltelevision signals is sufficient for digital television reception, thisrobustness may not be sufficient for the transmission of auxiliary data,particularly where the auxiliary data are critical. Accordingly, one ofthe applications of the present invention is the transmission ofauxiliary data in a VSB format with outer encoding for added robustness.The auxiliary data transmitted in accordance with the application of thepresent invention are referred to herein as robust VSB data (RVSB)

SUMMARY OF THE INVENTION

[0007] In one aspect of the present invention, a method for providingenhanced slice prediction comprises the following: receiving an inputcontaining first and second data, wherein the first and second data havedifferent bit rates and are defined by the same n level constellation;decoding only the second data with a decoder; producing an output inresponse to the input and the decoder, wherein the output is confined toat least one but fewer than n/2 of the n constellation levels, andwherein n>2; and, providing the output as the enhanced slice prediction.

[0008] In another aspect of the present invention, an apparatus forproviding enhanced slice prediction comprises an inner decoder, an outerdecoder, and an enhanced slice predictor, The inner decoder innerdecodes a received signal to provide an inner decoded output. The innerdecoder produces n/2 possible decoding states based upon the receivedsignal, and the received signal contains data having n levels, whereinn>2. The outer decoder outer decodes the inner decoded output. Theenhanced slice predictor chooses at least one but fewer than the n/2 ofthe n/2 possible decoding states based upon an output of the outerdecoder and provides the chosen state or states as the enhanced sliceprediction.

[0009] In yet another aspect of the present invention, an apparatus forproviding enhanced slice prediction comprises an inner decoder, an outerdecoder, and an enhanced slice predictor. The inner decoder innerdecodes a received signal containing first and second data to provideinner decoded first and second data. The outer decoder outer decodesonly the second data. The enhanced slice predictor provides a predictionoutput based upon the first data when the second data is not availableand based upon the outer decoded second data when the second data isavailable.

BRIEF DESCRIPTION OF THE DRAWING

[0010] These and other features and advantages will become more apparentfrom a detailed consideration of the invention when taken in conjunctionwith the drawing in which:

[0011]FIG. 1 shows a robust VSB transmitter for transmitting robust VSBdata and ATSC data in accordance with the present invention;

[0012]FIG. 2 shows a standard ATSC receiver for receiving the ATSC datatransmitted by the robust VSB transmitter of FIG. 1;

[0013]FIG. 3 shows a robust VSB receiver for receiving the robust VSBdata transmitted by the robust VSB transmitter of FIG. 1;

[0014]FIG. 4 shows the ⅔ rate encoder of FIG. 1 in additional detail;

[0015]FIG. 5 shows the mapping function performed by the mapper of FIG.4;

[0016]FIG. 6 shows the operation of the ⅔ rate decoders of FIGS. 2 and3;

[0017]FIG. 7 shows another robust VSB transmitter for transmittingrobust VSB data and ATSC data in accordance with the present invention;

[0018]FIG. 8 shows a standard ATSC receiver for receiving the ATSC datatransmitted by the robust VSB transmitter of FIG. 7;

[0019]FIG. 9 shows a robust VSB receiver for receiving the robust VSBdata transmitted by the robust VSB transmitter of FIG. 7;

[0020]FIG. 10 shows a circuit for generating the appropriate controlsignal on the discard control line of FIG. 9;

[0021]FIG. 11 shows yet another robust VSB transmitter for transmittingrobust VSB data and ATSC data in accordance with the present invention;

[0022]FIG. 12 shows an example of four data segments containing ½ rateouter coded data that may be transmitted by a robust VSB transmitteraccording to the present invention;

[0023]FIG. 13 shows an example of four data segments containing ¼ rateouter coded data that may be transmitted by a robust VSB transmitteraccording to the present invention;

[0024]FIG. 14 shows an example of four data segments containing ¾ rateouter coded data that may be transmitted by a robust VSB transmitteraccording to the present invention;

[0025]FIG. 15 shows the interleavers (I_(r)) of FIGS. 1, 9, and 11 inmore detail;

[0026]FIG. 16 shows the deinterleavers (D_(r)) of FIGS. 3 and 9 in moredetail;

[0027]FIG. 17 shows a map definition structure of a first robust VSBdata packet of a frame;

[0028]FIG. 18 shows a portion of the frame sync segment of a frame thatcarries a map indicating where in the frame robust VSB data can befound;

[0029]FIG. 19 illustrates an enhanced slice predictor according to oneembodiment of the present invention;

[0030]FIG. 20 shows the trellis for the inner decoder of FIG. 19;

[0031]FIG. 21 shows possible state transitions for the outer decoder ofFIG. 19; and,

[0032]FIG. 22 illustrates an enhanced slice predictor according toanother embodiment of the present invention.

DETAILED DESCRIPTION RVSB and ATSC Data Transmission and Reception

[0033]FIG. 1 shows a robust VSB transmitter 10 that transmits both ATSCdata and robust VSB data in accordance with one embodiment of thepresent invention. FIG. 2 shows a standard ATSC receiver 12 thatreceives the ATSC data transmitted by the robust VSB transmitter 10, andFIG. 3 shows a robust VSB receiver 14 that receives the robust VSB datatransmitted by the robust VSB transmitter 10.

[0034] The robust VSB transmitter 10 includes a Reed/Solomon encoder 16that encodes uncoded auxiliary data bytes by adding Reed/Solomon paritybytes to the uncoded auxiliary data bytes. The uncoded auxiliary databytes and the Reed/Solomon parity bytes are interleaved by aninterleaver 18. Then, the interleaved uncoded auxiliary data bytes andthe Reed/Solomon parity bytes are bitwise encoded by an outer coder 20using either a convolutional code or other error correcting code. Theouter coder 20 improves the robustness of the uncoded auxiliary databytes and the Reed/Solomon parity bytes, converting them to robust databytes (hereinafter referred to as robust VSB data bytes) andReed/Solomon parity bytes.

[0035] The outer coder 20, for example, may be a ½ rate coder whichproduces two output bits for every input bit, a ¼ rate coder whichproduces four output bits for every input bit, or a ¾ rate coder whichproduces four output bits for every three input bits. Other coders couldinstead be used. At the output of the outer coder 20, a three bytetransport (tx) header is added to each group of 184 coded robust VSBdata and Reed/Solomon bytes to form robust VSB data packets. Amultiplexer 24 multiplexes these robust VSB data packets with ATSC datapackets (typically, video and audio) each comprising a three bytetransport header and 184 bytes of ATSC data. Either input to themultiplexer 24 may be selected on a packet by packet basis and eachselected input is supplied to an ATSC transmitter 26. The selection bythe multiplexer 24 of which input to pass to the ATSC transmitter 26 isbased on a robust VSB map to be described hereinafter.

[0036] The ATSC transmitter 26, as is typical, includes a Reed/Solomonencoder 28, an interleaver 30, and a ⅔ rate inner encoder 32 alloperating in accordance with the ATSC standard.

[0037] A standard ATSC receiver, such as the standard ATSC receiver 12shown in FIG. 2, receives and processes the ATSC data and discards therobust VSB data. Accordingly, the standard ATSC receiver 12 includes a ⅔rate inner decoder 34, a deinterleaver 36, and a Reed/Solomon decoder38, all operating in accordance with the ATSC standard. The standardATSC receiver 12, however, is programmed to decode both the ATSC dataand the robust VSB data transport headers (which include the packetidentifications or PID's and which have not been coded by the outercoder 20). The standard ATSC receiver 12 reads the PID's of all packetsand, at 40, discards those packets having the PID's of robust VSB data.The standard ATSC receiver 12 also includes a slice predictor 42 (suchas the slice predictor disclosed in U.S. Pat. No. 5,923,711) which isresponsive to the inner decoded data and which provides an output backto a phase tracker and/or equalizer, as is known in the art.

[0038] The robust VSB data packets can be received, decoded, andprocessed by a robust VSB receiver such as the robust VSB receiver 14shown in FIG. 3. As is known, and as shown in FIG. 4, the ⅔ rate innerencoder 32 of the ATSC transmitter 26 includes a precoder 44 and a fourstate trellis encoder 46. In combination, the precoder 44 and the fourstate trellis encoder 46 may be viewed as an eight state coder thatproduces three trellis encoded output bits (Z0 Z1 Z2) for every twoinput bits (X1 X2). A mapper 48 maps the three trellis encoded outputbits to a symbol having one of eight levels as shown in FIG. 5. As iswell known from convolutional code theory, the operation of the precoder44 and the four state trellis encoder 46 may be viewed as an eight state4-ary trellis.

[0039] Therefore, in the robust VSB receiver 14, a ⅔ rate inner decoder50 may operate on an eight state 4-ary trellis which views the precoder44 and the four state trellis encoder 46 of the ⅔ rate inner encoder 32in combination as shown in FIG. 6 to produce a soft output decision(using, for example, the SSA algorithm as described in “Optimum SoftOutput Detection for Channels with Intersymbol Interference,” Li,Vucetic, and Sato, IEEE Transactions on Information Theory, May, 1995).This soft decision making operation is more complicated than the widelyused Viterbi algorithm, which produces a hard decision output, but thesoft decision making operation more fully takes advantage of the codinggain provided by the outer coder 20.

[0040] The output of the ⅔ rate inner decoder 50 is deinterleaved by adeinterleaver 52. The robust VSB receiver 14 reads the PID's of allpackets at the output of the deinterleaver 52. Based upon these PID's,the robust VSB receiver 14 discards those packets at 54 which have thePID's of ATSC data and also discards the transport headers addedfollowing the outer coder 20 and the parity bytes added by theReed/Solomon encoder 28. Thus, the robust VSB receiver 14, at 54, passesonly the robust VSB data packets containing the robust VSB data coded bythe outer coder 20. The robust VSB data packets are decoded by an outerdecoder 56, deinterleaved by a deinterleaver 58 (which is the inverse ofthe interleaver 18), and Reed/Solomon decoded by a Reed/Solomon decoder60 in order to reconstruct the original uncoded auxiliary data suppliedto the Reed/Solomon encoder 16 of FIG. 1.

[0041] The reliable output of the outer decoder 56 (either soft or hardoutput may be used) is interleaved by an interleaver 62 (correspondingto the interleaver 30) in a feedback path 64 in order to restore theordering of the outer decoded data to the order of the data in thechannel. This interleaved outer decoded data can be used, for example,by a slice predictor 66 to create reliable feedback to a phase trackerand/or equalizer. However, the overall feedback delay introduced by thedeinterleaver 52 and the interleaver 62 in the robust VSB receiver 14 isgenerally too long to provide useful feedback to the phase trackerand/or equalizer.

[0042] The arrangement shown in FIGS. 7, 8, and 9 avoids the feedbackdelay introduced by the deinterleaver 52 and the interleaver 62 of therobust VSB receiver 14. FIG. 7 shows a robust VSB transmitter 80 inwhich uncoded auxiliary data bytes are encoded by a Reed/Solomon encoder82 which adds Reed/Solomon parity bytes to the uncoded auxiliary databytes. The uncoded auxiliary data bytes and the Reed/Solomon paritybytes are interleaved by an interleaver 84. Then, the interleaveduncoded auxiliary data bytes and Reed/Solomon parity bytes are bitwiseencoded by an outer coder 86 using either a convolutional code or aturbo product code, as discussed above. The bitwise output of the outercoder 86 is small block interleaved by a small block interleaver 88 inorder to reduce the impact of channel burst errors on the outerdecoding. The data provided by the small block interleaver 88 may bereferred to as Rdata(n.o.) which stands for normally ordered robust VSBdata.

[0043] One input of a first multiplexer 92 receives ATSC formattedpackets each comprising (i) a valid three byte transport header with aPID number for robust VSB data, (ii) 184 placeholder bytes of dummyrobust VSB data, and (iii) twenty placeholder bytes for dummy ATSCReed/Solomon parity data. The other input of the first multiplexer 92receives ATSC formatted dummy packets each comprising 207 bytes of dummyATSC data. These ATSC formatted dummy packets serve as placeholders forthe real ATSC packets to be added downstream. The inputs of the firstmultiplexer 92 may be selected on a packet by packet basis, and thisselection is based on the robust VSB map to be described later.

[0044] The selected output of the first multiplexer 92 is interleaved byan interleaver 94 according to the ATSC Standard for the convolutionalbyte interleave. A data replacer 96 receives both the output of theinterleaver 94 and the output of the small block interleaver 88. Thedata replacer 96 replaces each dummy robust VSB data placeholder bytefrom the interleaver 94 with the next normally ordered robust VSB databyte from the small block interleaver 88.

[0045] The output of the data replacer 96 contains normally orderedrobust VSB data with interspersed transport headers, dummy ATSCReed/Solomon parity bytes, and dummy ATSC data packet bytes. Adeinterleaver 98, which operates according to the ATSC Standard for bytedeinterleaving, deinterleaves the output of the data replacer 96 to thuseffectively “repacketize” the data as packets of transport headers,reordered robust VSB data (Rdata(r.o.)), dummy ATSC Reed/Solomon paritybytes, and dummy ATSC data. The reordering of the normally reorderedrobust VSB data results from the deinterleaving of the deinterleaver 98and the reordered data may be referred to as reordered robust VSB data.

[0046] The dummy ATSC Reed/Solomon parity bytes (20 per packet) of therobust VSB packets and the dummy ATSC data packets (207 bytes perpacket) are discarded at 100. The remaining robust VSB packets, eachincluding a transport header and reordered robust VSB data, aremultiplexed by a second multiplexer 102 with real ATSC data packets eachcontaining 187 bytes of a transport header and ATSC data. Either inputto the second multiplexer 102 may be selected on a packet by packetbasis and is supplied to an ATSC transmitter 104. The selection by thesecond multiplexer 102 of which input to pass to the ATSC transmitter104 is based on the robust VSB map to be described hereinafter.

[0047] The ATSC transmitter 104 typically includes a Reed/Solomonencoder 106, an interleaver 108, and a twelve way ⅔ rate inner encoder110 all operating in accordance with the ATSC standard. The Reed/Solomonencoder 106 outputs packets of transport headers, reordered robust VSBdata, and ATSC Reed/Solomon parity bytes multiplexed with packets oftransport headers, ATSC data, and ATSC Reed/Solomon parity bytes. TheATSC Reed/Solomon parity bytes for the robust VSB data are calculatedbased on the reordered robust VSB data. Moreover, the interleaver 108changes the ordering of the robust VSB data so that the robust VSB dataat the output of the interleaver 108 is again normally ordered robustVSB data. Also, the interleaver 108 disperses the transport headers, theATSC Reed/Solomon parity bytes, and the ATSC data. This data is ⅔ ratecoded by the twelve way ⅔ rate inner encoder 110 and is transmitted. Thetransmitted robust VSB data is in normal order, i.e., the order providedat the output of the small block interleaver 88. This normal orderpermits the robust VSB receiver to avoid the delay caused by thedeinterleaver 52 and the interleaver 62 of the robust VSB receiver 14.

[0048] As shown in FIG. 8, a standard ATSC receiver 120 includes atwelve way ⅔ inner decoder 122 which decodes the transmitted data toprovide an output data stream comprising normally ordered robust datawith interspersed transport headers ATSC data, and ATSC Reed/Solomonparity bytes located according to the ATSC convolutional byte interleaveprovided by the interleaver 108. An ATSC deinterleaver 124 restores thetransport headers, ATSC data, and ATSC Reed/Solomon parity bytes totheir transport “packetized” positions. Also, the ATSC deinterleaver 124converts the normally ordered robust VSB data into reordered robust VSBdata. This reordered form permits an ATSC Reed/Solomon decoder 126 ofthe standard ATSC receiver 120 to correctly test parity for the robustVSB data packets. The standard ATSC receiver 120 can then read therobust VSB data packet transport headers and gracefully discard therobust VSB data packets at 128 based on their PIDs.

[0049] As shown in FIG. 9, a robust VSB receiver 130 includes a softoutput twelve way ⅔ rate inner decoder 132. (A hard output ⅔ decoderwould result in a considerable loss of coding gain). The output of thesoft output twelve way ⅔ rate inner decoder 132 comprises normallyordered robust VSB data, with reordered ATSC data, transport headers,and ATSC Reed/Solomon parity symbols dispersed within the robust VSBdata at locations indicated by a discard control line 134 discussedbelow. A discard block 136, under control of the discard control line134, discards the reordered ATSC data, transport headers, and ATSCReed/Solomon parity symbols.

[0050] A small block deinterleaver 138 deinterleaves the robust VSBdata. The small block deinterleaver 138 has a relatively low delay time.This deinterleaving disperses possible burst errors in the robust VSBdata at the output of the soft output twelve way ⅔ rate inner decoder132. The normally ordered robust VSB data is bitwise decoded by an outerdecoder 140 which also packs the robust VSB data into bytes. The ampinformation telling the outer decoder 140 what decoding rate to use onwhat data is provided to the outer decoder 140 at an R_(MAP) Data input.Neither the deinterleaver 52 nor the interleaver 62 is needed in therobust VSB receiver 130 allowing for lower overall feedback delay to thephase tracker and/or equalizer. The outer decoded data can be used, forexample, by an enhanced slice predictor 142 to generate feedback to thechase tracker and/or equalizer. If desired, the feedback may be gated,or the step size of the equalizer gradient algorithm adjustedproportionally to the reliability of the decoded data.

[0051] The robust VSB data packet payload decoded by the outer decoder140 is deinterleaved by a deinterleaver 144 (which is the inverse of theinterleaver 84) and is Reed/Solomon decoded by a Reed/Solomon decoder146 (corresponding to the Reed/Solomon encoder 82) in order toreconstruct the original uncoded auxiliary data supplied to theReed/Solomon encoder 82 of FIG. 7.

[0052] As provided in the ATSC standard, a frame comprises a pluralityof segments each containing a predetermined number of bytes. The firstsegment of a frame is a frame sync segment, and the remaining segmentsin the frame are data segments. Although robust VSB data can betransmitted in segments or in partial segments, it is convenient totransmit robust VSE data in segment pairs. The robust VSB map discussedabove indicates which segment pairs contain robust VSB data so that thediscard block 136 can correctly discard the reordered ATSC data beforethe reordered ATSC data can get to the outer decoder 140. The transportheaders and the ATSC Reed/Solomon parity data for all segments (robustVSB and ATSC) must also be discarded by the discard block 136.

[0053] A conceptually simple circuit to generate the appropriate controlsignal on the discard control line 134 to control this discardingfunction is shown in FIG. 10, together with the relevant portion of therobust VSB receiver 130. The robust VSB receiver 130 uses received mapinformation (the method for transmission and reception of this mapinformation is described below) to instruct a dummy segment generator150 when to construct dummy 207 byte segments. The dummy segmentgenerator 150 also uses the frame sync signal. For each ATSC dummysegment, the dummy segment generator 150 sets all bytes to FF. For eachrobust VSB data dummy segment, the dummy segment generator 150 sets thetransport header and ATSC Reed/Solomon parity bytes to FF. The dummysegment generator 150 sets the rest of the bytes of each robust VSB datadummy segment to 00.

[0054] These dummy segments are fed by the dummy segment generator 150to an ATSC convolutional byte interleaver 152 whose output is then usedto control the discard block 136 which then responds to the FF and 00codes to correctly discard the reordered ATSC data, the transportheaders, and the ATSC Reed/Solomon parity data which are interleavedwithin the received data stream. The discard block 136, thus, passesonly the robust VSB data.

[0055]FIG. 11 shows a multiple outer code robust VSB transmitter 160.The robust VSB transmitter 160 operates similarly to the robust VSBtransmitter 80 of FIG. 7. The robust VSB transmitter 160 has a firstReed/Solomon encoder 162 which encodes first uncoded auxiliary data byadding Reed/Solomon parity bytes to the first uncoded auxiliary data, asecond Reed/Solomon encoder 164 which encodes second uncoded auxiliarydata by adding Reed/Solomon parity bytes to the second uncoded auxiliarydata, and a third Reed/Solomon encoder 166 which encodes third uncodedauxiliary data bytes by adding Reed/Solomon parity bytes to the thirduncoded auxiliary data. The Reed/Solomon encoded first uncoded auxiliarydata are interleaved by a first interleaver 168, the Reed/Solomonencoded second uncoded auxiliary data are interleaved by a secondinterleaver 170, and the Reed/Solomon encoded third uncoded auxiliarydata are interleaved by a third interleaver 172. Then, the interleavedReed/Solomon encoded first uncoded auxiliary data are bitwise encoded bya first outer coder 174, the interleaved Reed/Solomon encoded seconduncoded auxiliary data are bitwise encoded by a second outer coder 176,and the interleaved Reed/Solomon encoded third uncoded auxiliary dataare bitwise encoded by a third outer coder 178. The bitwise output ofthe first outer coder 174 is interleaved by a first small blockinterleaver 180, the bitwise output of the second outer coder 176 isinterleaved by a second small block interleaver 182, and the bitwiseoutput of the third outer coder 178 is interleaved by a third smallblock interleaver 184.

[0056] The first outer coder 174 is a ¼ rate coder, the second outercoder 176 is a ½ rate coder, and the third outer coder 178 is a ¾ ratecoder, although any other combination of these or other outer codersusing different coding rates could be used. The data outputs of thefirst, second, and third small block interleavers 180, 182, and 184 areselected by a multiplexer 186 under control of a select input whichdetermines the order in which the differently outer coded data areinserted into the frame to be transmitted. The data at the output of themultiplexer 186 may be referred to as Rdata(n.o.) which, as before,stands for normally ordered robust VSB data.

[0057] The top three inputs of a multiplexer 190 receive ATSC formatpackets each having of a valid three byte transport header with a PIDnumber for robust VSB data, 184 placeholder bytes of dummy robust VSBdata, and twenty dummy placeholder bytes for ATSC Reed/Solomon paritydata. The robust VSB data at the topmost input of the multiplexer 190correspond to ¼ rate coded data from the first outer coder 174, therobust VSB data at the next input of the multiplexer 190 correspond to ½rate coded data from the second outer coder 176, and the robust VSB dataat the next input of the multiplexer 190 correspond to ¾ rate coded datafrom the third outer coder 178. The data supplied to the bottommostinput of the multiplexer 190 comprises ATSC format dummy packets eachhaving 207 bytes of dummy ATSC data. These dummy ATSC data packets serveas placeholders for the real ATSC data packets to be added downstream ofthe multiplexer 190. The inputs to the multiplexer 190 may be selectedon a packet by packet basis in accordance with the input on a selectline. This selection is based on the robust VSB data map to be describedbelow.

[0058] The output of the multiplexer 190 is interleaved by aninterleaved 192 in order to achieve a correct ATSC convolutionalinterleave. A data replacer 194 receives both the output of theinterleaver 192 and the output of the multiplexer 186. The data replacer194 replaces each dummy robust VSB data placeholder byte from themultiplexer 190 with the next corresponding normally ordered robust VSBdata byte from the multiplexer 186.

[0059] The output of the data replacer 194 contains normally orderedrobust VSB data (which is ¼ rate coded, ½ rate coded, and/or ¾ ratecoded, as appropriate) with interspersed transport headers, dummy ATSCReed/Solomon parity bytes, and dummy ATSC data packet bytes. Aconvolutional byte deinterleaver 196 (as described in the ATSC Standard)deinterleaves the output of the data replacer 194 to thus effectively“repacketize” the data as packets of transport headers, reordered robustVSB data (¼,½, and/or ¾ rate coded), dummy ATSC Reed/Solomon paritybytes, and dummy packets of ATSC data. The reordering of the normallyordered robust VSB data results from the deinterleaving of thedeinterleaver 196.

[0060] The dummy ATSC Reed/Solomon parity bytes (20 per packet) and thedummy ATSC data packets (207 bytes per packet) are discarded at 198 in amanner similar to that provided by the discard control line 134 and thediscard block 136 of FIG. 9. The remaining robust VSB packets, eachincluding a transport header and reordered robust VSB data, aremultiplexed by a multiplexer 200 with real ATSC data packets eachcontaining 187 bytes of a transport header and ATSC data. Either inputto the multiplexer 200 may be selected on a packet by packet basis andis supplied to an ATSC transmitter 202. The selection by the multiplexer200 of which input to pass to the ATSC transmitter 202 is based on therobust VSB map to be described hereinafter.

[0061] The ATSC transmitter 202 typically includes a Reed/Solomonencoder 204, an interleaver 206, and a twelve way ⅔ rate inner encoder208 all operating in accordance with the ATSC standard. The Reed/Solomonencoder 204 outputs packets of transport headers, reordered robust VSBdata, and ATSC Reed/Solomon parity bytes multiplexed with packets oftransport headers, ATSC data, and ATSC Reed/Solomon parity bytes. TheATSC Reed/Solomon parity bytes for the robust VSB data are calculatedbased on the reordered robust VSB data. Moreover, the interleaver 206changes the ordering of the robust VSB data so that the robust VSB dataat the output of the interleaver 206 are again normally ordered robustVSB data. Also, the interleaver 206 disperses the transport headerbytes, the ATSC Reed/Solomon parity bytes, and the ATSC data. These dataare ⅔ rate coded by the twelve way ⅔ rate inner encoder 208 and aretransmitted. The transmitted robust VSB data are in normal order, i.e.,the order provided at the output of the multiplexer 186. This normaldata order permits the robust VSB receiver to avoid the delay caused bythe deinterleaver 52 and the interleaver 62.

[0062] As discussed above, an ATSC frame comprises a frame sync segmentand a plurality of data segments and, for convenience, robust VSB dataare packed into groups of four segments. More specifically, FIG. 12shows an example of four data segments that may be used in a frame totransmit robust VSB data that is ½ rate coded, FIG. 13 shows an exampleof four data segments that may be used in a frame to transmit robust VSBdata that is ¼ rate coded, and FIG. 14 shows an example of four datasegments that may be used in a frame to transmit robust VSB data that is¾ rate coded. These examples represent the frame prior to theinterleaver 108 and assume that each group of four robust VSB datasegments contains an integral number of robust Reed/Solomon encodedblocks each of which is 184 bytes long, of which twenty bytes are paritybytes.

[0063] For the case of a ½ rate outer code, FIG. 12 shows that the outercoder outputs two bits for each input bit. A robust VSB data packet ispacked as one RVSB Reed-Solomon block to a pair of data segments (onebit per symbol) so that, for a ½ rate outer code, four segments containtwo robust Reed/Solomon encoded blocks. As shown in FIG. 13, for thecase of a ¼ rate outer code, the outer coder outputs four bits for eachinput bit. Robust VSB data is packed as one RVSB Reed-Solomon block forevery four data segments (½ bit per symbol) so that, for a ¼ rate outercode, four segments contain one robust Reed/Solomon encoded block. Asshown in FIG. 14, for the case of a ¾ rate outer code, the outer coderoutputs four bits for each three input bits. In this case, transmittedsymbol and byte boundaries do not always match. However, three completeRVSB Reed-Solomon blocks will pack exactly into four data segments (1.5bits per symbol) so that, for a ¾ rate outer code, four segments containthree robust Reed/Solomon encoded blocks.

[0064] Accordingly, FIGS. 12, 13, and 14 can be represented by thefollowing table: S X Y ½ 1 2 ¼ 1 4 ¾ 3 4

[0065] where X represents the number of complete robust Reed/Solomonencoded blocks and Y represents the number of frame segments required tocontain the corresponding number X of robust Reed/Solomon encodedblocks.

[0066] However, it should be understood that other coding rates can beused in conjunction with the present invention and, therefore, the abovetable will change depending upon the particular coding rates that areused.

[0067] The interleavers 18, 84, 168, 170, and 172 are shown in moredetail in FIG. 15, and the deinterleavers 58 and 144 are shown in moredetail in FIG. 16, assuming that a robust Reed/Solomon encoded block ischosen to be 184 bytes long. The interleavers 18, 84, 168, 170, and 172are B=46, M=4, N=184 convolutional interleavers that byte wiseinterleave the robust VSB data. This interleaving scheme is the same asthe ATSC interleaver scheme described in the ATSC Digital TelevisionStandard A/53 and the Guide to the Use of the ATSC digital TelevisionStandard A/54, except that the B parameter for the robust interleaver is46 instead of 52 and the parameter N is 184 instead of 208. Thisinterleaver is needed so that a robust VSB receiver can cope with longbursts of noise on the channel even though the ATSC deinterleaver(D_(a)) is bypassed as shown in FIG. 9.

[0068] As shown in FIG. 16, the deinterleavers 58 and 144 are B=46, M=4,N=184 convolutional deinterleavers that byte wise deinterleave therobust VSB data. This deinterleaving scheme is also the same as the ATSCdeinterleaver scheme described in the ATSC Digital Television StandardA/53 and the Guide to the Use of the ATSC digital Television StandardA/54, except that the B parameter for the robust deinterleaver is 46instead of 52 and the parameter N is 184 instead of 208.

[0069] Because a robust VSB Reed/Solomon block comprises 184 bytes, andbecause an integral number of robust VSB Reed/Solomon blocks are in adata frame, the number of robust VSB data bytes plus robust VSBReed/Solomon parity bytes in a data frame is always evenly divisible by46. Therefore, the frame sync segment can be used as a synchronizer forthe deinterleavers 58 and 144 (D_(r)) in the receiver, regardless of thevalue of G (to be described below). At frame sync, the deinterleavercommutators are forced to the top positions. The deinterleavers 58 and144 are byte wise deinterleavers.

Data Mapping

[0070] As discussed above, each data frame may contain a mix of robustVSB data segments and ATSC (non-robustly coded) data segments. Moreover,the robust VSB data may contain data coded with a mix of coding rates.The robust VSB receiver 14 or 130 must have a robust VSB map thatindicates which segments are robust VSB coded and which outer code isused for the robust VSB coding so that the robust VSB receiver 14 or 130can correctly process the robust VSB data and discard the ATSC data. Therobust VSB transmitters 10, 80, and 160 also use the robust VSB map tocontrol their corresponding multiplexing and discard functions. Thisrobust VSB map is transmitted by the robust VSB transmitter 10, 80, or160 to the robust VSB receiver 14 or 130 along with all the other datain a manner described below.

[0071] The presence, amount, and location of the robust VSB data in adata frame encoded with a particular outer code are indicated by one ormore numbers S_(C) that appear as two level data in the frame syncsegment of the data frame. As is known, the frame sync segment is thefirst segment in a frame. So, for the outer codes described above (¼rate, ½ rate, and ¾ rate), the frame sync segment should preferablycontain [S_(¼) S_(½) S_(¾)]. Each S_(c) (such as S_(¼) or S_(½) orS_(¾)) is encoded as eighteen symbols (bits) of two level data. For allthree codes, a total of 3×18=54 symbols are needed as a definition ofthe robust VSB map. These symbols are inserted into the reserved areanear the end of each frame sync segment (just before the twelveprecoding bits). For each group of eighteen bits (b₁₈ . . . b₁), thelast six bits (b₆ . . . b₁) represent the number G of groups of eightsegments (8 segments=2, 4 or 6 robust VSB data packets depending on theouter code) mapped as robust VSB data in the current frame. The twelvepreceding bits are for comb filter compensation (see the Guide to theUse of the ATSC digital Television Standard A/54). Accordingly, as shownin FIG. 18, bits b₆ . . . b₁, represent the number G, bits b₁₈ . . . b₁₃are the complement of bits b₆ . . . b₁, and bits b₁₂ . . . b₇ can bealternating +1 and −1 (or any other pattern).

[0072] Let it be assumed that S=S_(¼)+S_(½)+S_(¾). Because 312/8=39,0-39 groups of eight segments can be mapped as robust VSB data or 8 VSBdata (ATSC data). Therefore, each S_(C) may have a value of 0 . . . 39,as long as their sum S is≦39.

[0073] The robust VSB data segments are preferably distributed asuniformly as possible over the data frame. For example, if S=1, then thefollowing eight segments are mapped as robust VSB data segments and allother segments are mapped as ATSC data segments: 1, 40, 79, 118, 157,196, 235, and 274. If S=2, then the following sixteen segments aremapped as robust VSB data segments and all other segments are mapped asATSC data segments: 1, 20, 39, 58, 77, 96, 115, 134, 153, 172, 191, 210,229, 248, 267, and 286. These examples continue until S=39, where thewhole data frame is mapped as robust VSB data segments. For some valuesof S, the spacing between robust VSB data segment pairs is not perfectlyuniform. However, for any value of S, the spacing is fixed in advancedand, therefore, known to all receivers.

[0074] If a frame contains robust VSB data provided by three outercoders operating at ¼ rate, ½ rate, and ¾ rate, then the data from thesethree outer coders may be divided in a frame such that, as to RVSBsegments, the first 8×S_(¼) segments contain the ¼ rate outer codeddata, the next 8×S_(½) segments contain the ½ rate outer coded data, andthe last 8 ×S_(¾) segments contain the ¾ rate outer coded data. However,other robust VSB data segment organizations are possible for these threeouter coders or for any number of other types of outer coders.

[0075] Because this robust VSB map is contained in the frame syncsegment, as discussed above, the robust VSB map does not enjoy the samelevel of coding gain as the robust VSB data. However, the robust VSB mapmay still be reliably acquired by a robust VSB receiver by correlatingthe robust VSB map over some number of frames. Therefore, the robust VSBmap should not change too often (for example, not more often than every˜60 frames).

[0076] The above mapping method allows a receiver to reliably and simplyacquire the robust VSB map by correlation. Once a receiver has acquiredthe map, it is desirable for the receiver to instantly and reliablytrack changes in the map. In order to instantly and reliably trackchanges in the map, the definition in the robust VSB map for each outercode, excluding the comb compensation bits, is duplicated in the firstrobust VSB Reed/Solomon encoded block of the frame. In addition, thereis data indicating (i) when in the future the map will change and (ii)the future new map definition. The first robust VSB data packet of aframe for an outer coder, therefore, has the structure shown in FIG. 17,where the robust VSB map definition data is given by the following:eight bits designating the current map (only six of these bits areused); eight bits designating the number of frames until the map changes(1-125; if 0, then no change coming); and, eight bits designating thenext map (again, only six of these bits are used). The remaining portionof the first robust VSB data packet is data. The first RVSB segment in aframe for a respective outer coder has the arrangement shown FIG. 17.

[0077] In this way, a receiver can track map changes using reliablerobust VSB data. Even if a burst error destroys a number of the frames,the receiver can keep its own frame countdown using the number of framesread from a previously received frame. If the receiver finds at any timethat the definition for an outer code previously acquired by the framesync correlation does not match the definition for that outer code inthe first robust VSB data segment, the receiver should restart its mapacquisition process.

RVSB Enhanced Slice Prediction and Equalizer Feedback

[0078] ATSC 8 VSB receivers make important use of adaptive equalizationand phase tracking as explained in the ATSC Digital Television StandardA/53 published by the Advanced Television Systems Committee, in theGuide to the Use of the ATSC Digital Television Standard A/54, alsopublished by the Advanced Television Systems Committee. RVSB asdescribed above has features that allow for improvements in adaptiveequalization and phase tracking.

[0079] One such improvement results from feeding back delayed reliableestimates of the input symbol level to the adaptive equalizer and/orphase tracker based on a sequence estimation from an enhanced ViterbiAlgorithm. (See “The Viterbi Algorithm,” G. D. Forney, Jr., Proc. IEEE,vol 61, pp. 268-278, March, 1973). This type of feedback avoids the needfor “re-encoding,” which has a state initialization problem.

[0080] U.S. Pat. No. 5,923,711, entitled “Slice Predictor for a SignalReceiver,” discloses an ATSC 8 VSB receiver which utilizes a slicepredictor in order to provide more reliable feedback to the phasetracker or adaptive equalizer. This feedback can be made even morereliable by a enhanced slice predictor system 300 shown in FIG. 19. Theenhanced slice predictor system 300 has an inner decoder 302 and anouter decoder 304 which operate similarly to the inner decoders andouter decoders described above.

[0081] The slice prediction output from the inner decoder 302 works in amanner similar to that described in the aforementioned U.S. Pat. No.5,923,711. As explained above, the inner decoder 302 is based on an 8state 4-ary trellis that includes a precoder. Based on the best pathmetric at the current time t, the slice predictor of the inner decoder302 decides a most likely state at time t. Then, based on the nextpossible pair of states, four possible predicted input levels (out ofeight) for the next symbol at time t+1 are selected. For example, asshown by the inner decoder trellis in FIG. 20, if the most likely stateat time t is state one, the next state is ε[1 5 2 6]. Therefore, thenext input level at time t+1 may be−1,+1, -3, or +5, These next inputlevels correspond to decoded bit pairs 00, 10, 01, and 11, respectively.

[0082] Similarly, the outer decoder 304 also finds the best path metricfor the current time t for the respective trellis. A portion of thistrellis is shown in FIG. 21 for an exemplary outer decoder and may beapplied generally to all three outer codee. As shown in FIG. 21, twopossible outer decoder input bit pairs are selected for the time t+1based on the next possible pair of states. By way of example, the twopossible outer decoder input bit pairs may be 11 or 01. The bit pairchosen by the outer decoder 304 is sent to a prediction enhancer 306which selects amplitude levels +5 or −3 from the set of four levelspreviously selected by the slice predictor of the inner decoder 302 asthe enhanced slice prediction for time t+1. Because the slice predictionof the inner decoder 302 is near zero delay, but because the outerdecoder 304 cannot operate on the same symbol until after the innerdecoder 302 has provided a decoded soft output, a delay module 308provides a delay time slightly greater than the traceback delay time ofthe inner decoder 302. The slice prediction provided by the predictionenhancer 306 may be supplied as feedback to an equalizer of phasetracker 310.

[0083] With some additional delay time, the outer decoder 304 can make afinal hard decision and select a single most likely input bit pair fortime t+1. For example, if 11 is found to be the most likely input bitpair to the outer decoder 304 as determined by its Viterbi Algorithm,this information is sent by the outer decoder 304 to the predictionenhancer 306 which then chooses+5 from the set of four levels andcorresponding bit pairs already selected by the slice predictor of theinner decoder 302. The outer code can be a convolutional code or othertype of error correction code. The predictor enhancer 306 is disabledduring the periods of time when ATSC data is being received.

[0084] A feedback enhanced maximum likelihood sequence estimator (MLSE)slice predictor system 320 uses the Viterbi Algorithm and is shown inFIG. 22 along with other relevant parts of an RVSB receiver. Thefeedback enhanced MLSE slice predictor system 320 has an inner decoder322 and an cuter decoder 324 which operate similarly to the innerdecoder 302 and the outer decoder 304 described above. However, insteadof using the slice prediction output of the inner decoder 302, anenhanced MLSE module 326 is configured to execute the usual ViterbiAlgorithm on the received signal by operating the eight state ⅔ ratecode trellis (the same trellis used by the inner decoder 322, includingthe precoder).

[0085] The enhanced MLSE module 326 selects as its next input either (i)the noisy eight level received signal as delayed by a delay module 328if the next input is a non-RVSB symbol or (ii) the bit pair decisionoutput of the outer decoder 324 (hard or soft) if the next input is aRVSB symbol. The enhanced MLSE module 326 makes this selection accordingto the symbol by symbol information in the RVSB map.

[0086] The enhanced MLSE module 326 outputs one of eight possiblesymbols as its slice prediction, and this slice prediction (symboldecision) is provided by the enhanced MLSE module 326 as feedback to anequalizer or phase tracker 330.

[0087] The enhanced MLSE module 326 should follow a more correct paththrough the eight state trellis than does the inner decoder 322 becausethe enhanced MLSE module 326 gets more reliable input from the outerdecoder 324 when an RVSB symbol is available.

[0088] The output of the enhanced MLSE module 326 may be a hard slicedecision or a soft level. Also, any symbol reliability indication fromthe inner decoder 322 or the outer decoder 324 may be used to change thestep size of the equalizer LMS algorithm. (See the Guide to the Use ofthe ATSC Digital Television Standard A/54.)

[0089] An optional predetermined coded training sequence may be includedin a specified portion of the first RVSB segment of a data field. Thissequence is known in advance by both the transmitter and receiver.During the time the decoded training sequence is output from the outerdecoder 324, the input to the enhanced MLSE module 326 is switched to astored version of the decoded training sequence.

[0090] Certain modifications of the present invention have beendiscussed above. Other modifications will occur to those practicing inthe art of the present invention. For example, although the standardATSC receiver 12 and the robust VSB receiver 14 are shown above asseparate receivers, the functions of the standard ATSC receiver 12 andthe robust VSB receiver 14 can be combined in two data paths of a singlereceiver capable of decoding both types of data (ATSC data and robustVSB data).

[0091] Accordingly, the description of the present invention is to beconstrued as illustrative only and is for the purpose of teaching thoseskilled in the art the best mode of carrying out the invention. Thedetails may be varied substantially without departing from the spirit ofthe invention, and the exclusive use of all modifications which arewithin the scope of the appended claims is reserved.

1. A method for providing enhanced slice prediction comprising:receiving an input containing first and second data, wherein the firstand second data have different bit rates and are defined by the same nlevel constellation; decoding only the second data with a decoder;producing an output in response to the input and the decoder, whereinthe output is confined to at least one but fewer than n/2 of the nconstellation levels; and wherein n>2; and, providing the output as theenhanced slice prediction.
 2. The method of claim 1 wherein the decoderis a first decoder, wherein the receiving of an input comprises decodingthe input with a second decoder to recover the first and second data,wherein the second decoder has n states, wherein the producing of anoutput comprises choosing n/4 states out of n/2 states of the n statesof the second decoder, and wherein the providing of the output comprisesproviding the n/4 states as the enhanced slice prediction.
 3. The methodof claim 2 further comprising delaying the selection of the n/4 statesbased upon a processing time of the second decoder.
 4. The method ofclaim 1 wherein n is eight, wherein the decoder is a first decoder,wherein the receiving of an input comprises decoding the input with asecond decoder to recover the first and second data, wherein the seconddecoder has eight states, wherein the producing of an output compriseschoosing only two states out of four states of the eight states of thesecond decoder, and wherein the providing of the output comprisesproviding the two states as the enhanced slice prediction.
 5. The methodof claim 4 further comprising delaying the selection of the two statesbased upon a processing time of the second decoder.
 6. The method ofclaim 1 wherein n is eight, wherein the decoder is a first: decoder,wherein the receiving of an input comprises decoding the input with asecond decoder to recover the first and second data, wherein the seconddecoder has eight states, wherein the producing of an output compriseschoosing only one state out of four states of the eight states of thesecond decoder, and wherein the providing of the output comprisesproviding the one state as the enhanced slice prediction.
 7. The methodof claim 6 further comprising delaying the choosing of the one statebased upon a processing time of the second decoder.
 8. The method ofclaim 1 wherein the producing of an output comprises: decoding the inputwhen the second data is not available so as to produce the output; and,decoding the second data when the second data is available so as toproduce the output.
 9. The method of claim 8 further comprising delayingthe decoding of the input based at least in part upon a processing timeof the decoder.
 10. The method of claim 8 wherein the providing of theoutput as the enhanced slice prediction comprises providing only onestate as the enhanced slice prediction.
 11. The method of claim 8further comprising selecting between decoding the input and the seconddata in response to a received map.
 12. The method of claim 8 whereinthe first data comprises eight level non-RVSB symbols, and wherein thesecond data comprises eight level RVSB symbols.
 13. The method of claim8 wherein the providing of the output as the enhanced slice predictioncomprises providing the enhanced slice prediction based upon a knowntraining signal when a transmitted training signal is contained in areceived signal.
 14. The method of claim 1 wherein the decoder is afirst decoder, wherein the receiving of an input comprises decoding theinput with a second decoder to recover the first and second data,wherein the decoding of only the second data comprises decoding thesecond data with the first decoder to produce decoded second data, andwherein the producing of an output comprises; producing the output bydecoding the input with a third decoder when the decoded second data isnot available; and, producing the output by decoding the second decodeddata with the third decoder when the decoded second data is available.15. The method of claim 14 further comprising delaying the decoding ofonly the input.
 16. The method of claim 14 wherein the third decoderimplements a Viterbi algorithm.
 17. The method of claim 14 wherein theproviding of the output as the enhanced slice prediction comprisesproviding only one state of the third decoder as the enhanced sliceprediction.
 18. The method of claim 14 further comprising selectingbetween decoding the input and the decoded second data in response to areceived map.
 19. The method of claim 14 wherein the first datacomprises eight level non-RVSB symbols, and wherein the second datacomprises eight level RVSB symbols.
 20. The method of claim 14 whereinthe providing of the output as the enhanced slice prediction comprisesproviding the enhanced slice prediction based upon a known trainingsignal when a transmitted training signal is contained in a receivedsignal.
 21. The method of claim 1 further comprising providing theenhanced slice prediction as feedback to an equalizer.
 22. The method ofclaim 1 further comprising providing the enhanced slice prediction asfeedback to a phase tracker.
 23. The method of claim 1 wherein theproviding of the output as the enhanced slice prediction comprisesproviding the enhanced slice prediction based upon a known trainingsignal when a transmitted training signal is contained in a receivedsignal.
 24. An apparatus for providing enhanced slice predictioncomprising: an inner decoder that inner decodes a received signal toprovide an inner decoded output, wherein the inner decoder produces n/2possible decoding states based upon the received signal, wherein thereceived signal contains data having n levels, and wherein n>2; an outerdecoder that outer decodes the inner decoded output; and, an enhancedslice predictor that chooses at least one but fewer than the n/2 of then/2 possible decoding states based upon an output of the outer decoderand that provides the chosen state or states as the enhanced sliceprediction.
 25. The apparatus of claim 24 wherein n is eight, whereinthe enhanced slice predictor chooses two of the four possible statesbased upon the output of the cuter decoder, and wherein the enhancedslice predictor provides the chosen two states as the enhanced sliceprediction.
 26. The apparatus of claim 24 wherein n is eight, whereinthe enhanced slice predictor chooses two and only two of the fourpossible states based upon the output of the second decoder, and whereinthe enhanced slice predictor provides the chosen two and only two statesas the enhanced slice prediction.
 27. The apparatus of claim 24 whereinn is eight, wherein the enhanced slice predictor chooses one of the fourpossible states based upon the output of the outer decoder, and whereinthe enhanced slice predictor provides the chosen one state as theenhanced slice prediction.
 28. The apparatus of claim 24 wherein n iseight, wherein the enhanced slice predictor chooses one and only one ofthe four possible states based upon the output of the second decoder,and wherein the enhanced slice predictor provides the chosen one andonly one state as the enhanced slice prediction.
 29. The apparatus ofclaim 24 further comprising a delay that delays operation of theenhanced slice predictor based upon a processing time of the innerdecoder.
 30. The apparatus of claim 24 wherein the inner decoder is anATSC decoder, and wherein the outer decoder is an RVSB decoder.
 31. Theapparatus of claim 24 further comprising an equalizer coupled to receivethe enhanced slice prediction as feedback.
 32. The apparatus of claim 24further comprising a phase tracker coupled to receive the enhanced sliceprediction as feedback.
 33. An apparatus for providing enhanced sliceprediction comprising: an inner decoder that inner decodes a receivedsignal containing first and second data to provide inner decoded firstand second data; an outer decoder that cuter decodes only the seconddata; and, an enhanced slice predictor that provides a prediction outputbased upon the first data when the second data is not available andbased upon the outer decoded second data when the second data isavailable.
 34. The apparatus of claim 33 wherein the each of the firstand second data are 8 level symbols having different bit rates.
 35. Theapparatus of claim 33 wherein the enhanced slice predictor implements aViterbi algorithm.
 36. The apparatus of claim 33 wherein the predictionoutput is a single symbol.
 37. The apparatus of claim 33 furthercomprising a delay that delays operation of the enhanced slicepredictor.
 38. The apparatus of claim 33 wherein the first data arenon-RVSB symbols, and wherein the second data are RVSB symbols.
 39. Theapparatus of claim 33 wherein the first decoder is an ATSC decoder, andwherein the second decoder is an RVSB decoder.
 40. The apparatus ofclaim 33 further comprising an equalizer coupled to receive the enhancedslice prediction as feedback.
 41. The apparatus of claim 33 furthercomprising a phase tracker coupled to receive the enhanced sliceprediction as feedback.
 42. The apparatus of claim 33 wherein theenhanced slice predictor bases its slice prediction upon a knowntraining signal when a transmitted raining signal is contained in areceived signal.